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(No Model.) V 3 SheetsSheet 1.

G. G. BARTON & J. THOMSON. FLUID METER.

No. 313,159. Patented Mar. 3, 1885.

N. FETKRS Plmm Lum -when Washmglen. u. c.

(No Model.) 3 Sheets-Sheet -2. 0. O. BARTON 82 J, THOMSON FLUID METER.

Patented Mar. 3

N. PETERS. rhuwumo umm. Wnslvinglnn. n. c.

3 Sheets-Sheet 3;

(No Model.)

0. O'. BARTON& J. THOMSON FLUID METER.

Witnesses: 5 0

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CHARLES C. BARTON, OF NFHV YORK, AND JOI-Il\ THOMSON, OF BROOKLYN,N.Y.

FLUID-METER.

.JPBCIEFICATION forming part of Letters Patent No. 313,159, dated March 3, 1885.

Application filed Apri126, 1884. (No model.)

To ailwhom, it may concern.- Be it known that we, GHARIJES G. BARTON and J OHN THoMsoN, citizens of the United States, residing, respectively, in thecounty, city, and State of New York, and Brooklyn, county of Kings, and State of New York, have invented certain new and useful Improvements in Fluid- Meters, of which the following is a specification.

Our inventionrelates to fluid-meters of that class in which the displacement is obtained by the combination of a piston and diaphragm and a puppet-valve system. i

In general terms, the object of this invention is to produce an instrument which, in its working parts,shali approximate perfect equilibrium, requiring less power to operate, be ing more accurate in its measurement at all flows and pressures,and more durable, under long and severe service, than fluid-measu ring instruments heretofore produced.

To this end our invention refers particularly to the following features: first, the water-Ways, sluices, and ports, the formation of which is such as to establish as perfect and complete equilibrium in the operation of the valve and piston under hydrodynamic condifions as under hydrostatic conditions; second, the formation of said water-ways and sluices,

whereby to offer the minimum of frictional resistance to the flow of fluids; third, the manner of constructing the waterways; fourth,

' in animproved positive valveactuating mechanism whereby the said valve is thrown with such rapidity of movement that no appreciahis loss of fluid can occur during the transit of the valve, and also whereby there can be no increased travel of the piston at fast flows; fifth, in an improved form of valveretaining 43 spring; sixth, in an improved form and mode of constructing the valve and valvespindle; seventh, in an improved manner of constructing portions of the valve-chamber, and an improved form of the upper cylinder; eighth, in

a system of pressure-cones, whereby the strain of throwing the valve is transmitted by the diaphragm to said cones; and, ninth, in an improved manner of forming and constructing the piston.

In the drawings, Figure 1 is a vertical cen- 5o tral crosssection through the cylinder of our improved meter, exposing the valve-casing and the valve-actuating mechanism in side elevation. Fig. 2 is a top plan view of valvecasing and valve-actuating mechanism. Fig. 2 is a diagram of valve-retaining spring. Fig. 3 is an upright central crosssection through the cylinders, exposing the valve-casing and valve-actuating mechanism in front elevation, as viewed from the lefthand side of Fig. 1. Fig. 4 is a central cross-section of valve-casing 011 the line A of Fig. 2, showing the-valve in its alternative position. Figs. 5 and 6 are detached views, enlarged, of the valve and valve-spindle. Fig. 7 is a detached view of internal valve'seat and modifications of the same. Fig. 8 is a horizontal section th ough the water-ways and valvecasing on the lineC of Fig. 1, as viewed from below, with the operative mechanism removed. Fig. 9 is a detached elevation, in partial section of the pressure-cones; and Fig. 10 is a detached view of piston.

In order to produce an accurate-measuring and durable liquid-1neter, it is of the first and most vital importance that its operation shall be effected under conditions absolutely free from all extraneous influences, offering the least frictional retardation, and with a constant coefficient of friction, whatever he the pressure,or the volume, or the velocity of the flow.

In the usual practice heretofore the subject has been handled much as if it were a problemv in hydrostatics alone, while as a matter of fact it combines or should combine a complete blending of principles apparently well established both in hydrostatics and hydrodynamics. Thus, to illustrate, we have found that in the outcome of previous efforts in this direction,both of others and of 0urselves,while practically perfect measurements and generally satisfactory results were obtained at low velocity of flow, whether of small or great vol.- ume, both the measurement and the durability were unsatisfactory at ahigh velocity and great volume of flow. Therefore, in searchingfor the cause and the remedy, we have found that while the valve the vital part of a fluidmeterwould be perfectly balanced as to statical pressure, it would still be subjected to a portion of the force exerted by the motion of the fluid. Therefore, the sum of this force being directly as the velocity of the fluid and the area of the obstruction presented, and as the valve and its spindle ne'eessarilylie within one or more of the sluices or chambers traversed by the fluid, it will at once be apprehended that the power required to operate the valve will also vary directly as the velocity of flow in consequence of the friction developed in the bearings of the valve. We overcome this difficulty by neutralizing upon and by itself, at the valve and its ports, each and every current passing to the valve and from the valve which in any way can act to accelerate or to impede (by detrusion) the movement of the valve; hence as the force of thecurrent is expended upon itself at and around all portions of the valve it will be seen that its effect upon the valve is ml, and, furthermore, that the friction of the bearings of the valve will be a constant quantity-namely, that due to its weight. A construction whereby to attain this result is illustrated in the drawings, the operation and arrangement of which is as follows: Entering at the ingresspipe l,it will be seen that the fluid will be sub jected to an equal deflection and division at 2, and will pass both to the right and to theleft around the crown of the cylinder,through the ingress water-way 3, until the two currents thus formed reach the valvecasing 4. In said valve-casing is formed a longitudinal ingress-sluice, 5, which connects the two termini of the cylindrical water-way3, and thus completes the first circuit to the induction-port 6. (see Figs. 2 and 4,) where the two currents meet upon each other and pass the port as one current. 7 Again dividing after passing the port, it follows both to the right and to the'left, (as see arrows 8 9,) through the intermediate sluice, 7, ofthe valve-casing,to the two connecting intermediate water-ways, 10 ll, of the upper cylinder. The said water-Ways connect with corresponding water-ways,'12 13, in the lower cylinder. Thus this circuit is completed to thelower compartment, 14., formed by the piston 15 and diaphragm 16. The fluid beneath the piston and diaphragm will now act to expel the fluid fromthe upper compartment, 16, into and through the now open eduction-port 17,whence it will again find equal areas of exit through the egress-sluice 18 of the valve-casing, dividing and passing both to the right and to the left, connecting with and thereby completing the third and last circuit of the cylindrical egress waterway 19 of the cylinder to the egress-pipe 20. Upon the reversion of the valve to its alternative position assumed in i Fig. 4, the ingress-currents will again meet at the valve and valve-ports, but will pass the now open induction-port 21, the egress-current passing back through the intermediate sluice, (as see arrows 22 23,) through thenow open eduction-port 24, and thence out by equal deflections to the right and to the left, as before. Thus the current in the ingress portion of the valve-casing is neutralized with respect to the valve by continuous impact upon itself. In the intermediate sluice the current is neutralized by being alternately forced upon itself and forced asunder, while in the egresssluice the current is continuously forced asunder.

From the foregoing it will be apprehended that in whichever position the valve may be,

whether seated or in transit, the ingress, the intermediate, and the egress currents must necessarily draw away from or impinge upon each other at a right angle to the line ofmove. ment of the valve and upon the longitudinal center of the said valve, as the line 25, Fig. 8, and can therefore have no effect either to actuate the valve or to retard its movement, the valve, in fact, being subjected to two equal currents flowing in opposite directions.

It will be apparent that but slight modifications would be necessary in this arrangement of waterways to adapt the system to va rious styles of valves, and thatthe result will bethe same whether the passages be in the casing or in the valve, or in both.

The manner described of forming the waterways and sluices permits them to be made of large area and to be projected on arcs of long radii, hence, while the fluid may haveahigh veloci'ty through the pipe and ports, it-will pass with reduced speed, but without impediment,

through the water-ways and sluices. Furthermore, as no abrupt turns nor jogs are presented to the passing fluid,- it therefore suffers but very slight loss of head from direct frictional resistance to its flow.

In constructing the waterways in the cylinder it might be completely accomplished by coring. This, however, would complicate the process of molding and casting, as the core could only be supported where it opens to the pipe and to the valve-casing, besides which it would afterward be difficult to remove the core. We therefore prefer'to cast or core these water-ways with their lower portion partially open, as from 26 to 27, Fig. 8, coring out, however, where connecting with the valve-casing, as 28 29 30, as this leaves a solid surface from which to machine the taper and against which to place the valve-chamber. We then simply secure a plate or cover, as 31, over the open portions of the water-ways, making a water-tight joint, and the work is completed. In this way the molding and casting of the cylinder is of the simplest character, and the interior of the water-Ways may at any time be reached readily. The screws 32, which secure the valve-casing in position, are placed in the solid portions of the water-ways, as at 33.

The general arrangement of the valve-casing with respect to its attachment to the cyl- IIO inder and the mode of constructing it, the attachment of the face-plates 34, the piston-rod 35, the register apparatus, 8m, have had complete description in an accompanying separate application, and will therefore not require repetition herein, except as to certain modifications.

In the motor apparatus heretofore used to operate the valveusually actuated by a spring or weight-assuming the conditions of operation to be alike at slow and fast flows, the time required to throw the valve will be of the same duration at the slow flows as at the fast flows. The speed of the piston, however, at fast flows will have been greatlyincreased; hence while the displacement may be exact at the slow flows it will be increased-overrun-at fast flows. This is caused, first, by the increased travel of the piston, and, second, by the increased velocity of the fluid passing through the ports, the valve movement being constant,while the flow and velocity are variable; contrariwise of positive valve-actions, which may operate with comparative satisfaction at fast flows, but give most indifferent results, or are completely inoperative, at slow flows, in consequence of the valve not being shifted with sufficient rapidity, or not being set completely over to its proper alternative position; and when to'this is added a variable condition of operation, the case becomes more complex.

In View of the complete balance of ourvalve under every condition of operation, as hereinbefore described, we have been enabled to fully overcome the difficulties just cited, and

in the following manner:

Journaled at 36 on the same supporting arm, 37, extending from the valve-casing, as the bell=crank 38is what will be herein termed a multiplying-lever, 39, the extremity of which is engaged to the valvestern 40 by the slotted fork 41 and pin 42. The toggle-acting retainingsprings 43 exert their thrust between the thrust-block 44, fast to the valve stem, to the bearings 45 of the spring-carriage, to the bell-crank, and thence through the slotted arm 46 of the bell-crank to the tooth or spur 47 of the multiplying-lever. Thus the entire static energy of the springs is utilized in seating the valve.

In the position assumed in the figures the valve-actuating apparatus is in position to be operated upon the upstroke of the piston, during which stroke the piston-rod will engage the bellcrank and carry it upward.

It will be observed that the slot 48 of the arm of the bell-crank is wider than the tooth of the multiplying-lever which it strides, and, furthermore, that any motion which may be imparted to the multiplying-lever from the engagement of its tooth by the slotted arm will greatly augment the movement of said multiplying-lever at its point of engagement to the valvestem. The relation of the slot 48 to the tooth 47 is such that upon the continued movement of the bellcrank the sides of the slot will travel free of the tooth until just before or at the instant that the springs will have been brought to their dead-center, when a side of the slot will impinge upon the tooth. It will now be seen that the slightest additional move ment of the piston-rod will drive the multiplyinglever, and with it the valve-stem and valve, in an opposite direction to that of the point 49 of the bell-crank, and with much greater rapidity of movement. Meantime the springs are also acting upon the thrust-block of the valve-stem in the samedirection as the multiplying-lever, thereby adding their stored energy to that of the piston. To illustrate the action, assume the travel of the valve to be, say, .2 and the ratio of the movement of the multiplying-lever to that of the piston as five is to one. Then, without taking into consideration the effect of the springs, the piston'would only have to travel .04 to place the valve in its alternative position. (.2-'.- 5-:.04.)

Although the chief function of the springs is to hold the valve in contact with its seats, in consequence of which they require to excrt but slight force, they still assist to throw the valve, thus giving out in useful effect whatever sum of energy will have been stored within them by the piston in changing their direction of thrust upon the valve. This arrangement of the springs and bell-crank, while holding the valve positively to its seat until the exact instant at which it should be thrown, also at the same instant relieves the valve of all restraint, free to be acted upon by the multiplying-lever. There is thus no shock nor appreciable strain upon the diaphragm, piston, or connecting parts, either in reversing the thrust of the retaining-springs or in actuating the valve. The said multiplying-lever andslotted arm of bell-crank are preferably formed, as shown, to straddle their bearing, as in this way two slots and two teeth are obtained, which presents greater bearing-surface and centralizes' the strain during its operation. It will be obvious, however, that like effects may be had by'a different arrangement of levers. The slot might be formed in the multiplyinglever and the tooth on the arm of the bellcrank; but the arrangement shown is the better, as in this wise the strain is imparted to the multiplying-lever more nearly to the center line connecting the bearings of the bellcrank and said lever. Were the construction reversed, the strain would'then be applied off center at each alternative movement. springs 43 are formed somewhat like the letter 8 or a double inverted V. The advantage of this form over the plain V-springof previous use is that its tension and promptness of action are alike in either direction of thrust. As shown in the diagram 2, the V- spring, in consequence of its hinge-like movement from the center 49, will act more favorably when thrusting in the direction of the The arrow than in an opposite direction. In 6 the S or double V spring 43 the same defect exists, but is neutralized'upon itself, the hinge action of the wing 51 being in the direction of the arrow 52, while that of the wing 53 is in the opposite direction-arrow 54. The valve is constructed as shown in the enlarged figure, 5. Against the shoulder of the spindle 55 is first placed an annulus of fieXile packing, 56, as rubber, leather, &c.; next a thin cupped disk, 57, formed from spring metal, the cupped edge of which, 58, is slightly less in height than the thickness of the fiexile packing which it encompasses. Then a thin washer, 59, is interposed between another disk and packing,

. similar to the first pair, except that the cupped disk is reversed, thus placing the two packings outside, as shown. The spindle-bearing and shoulder is then screwed into the tapped bearing 61, and the valve is complete. Each portion of the valve is thus built up. By forming the metal disk in the manner aforesaid it is comparativelyrigid at its periphery, but is elastic and free to respond to any diaphragmatic action at its center, or as a ball and socket in some stages of movement.

The cupped or inverted portion also serves to protect the edge of the packing from being worn or collapsed by the impact of the currents through the valve-casing. The separation of thetwo disks by the washer 59 virtually provides a distinct valve for each valveseat; hence, while one valveface may be continuously deflected in one direction to adapt itself to some inaccuracy in its construction, or to some interposed foreign obstruction, it will have no tendency to transmit the error to the opposite face of the valve, which latter may be correct, or subject to deflection in different degree or different direction. This form of metal disk is also of great utility when used as a metal valve without packing, either with an increased bearing-surlace, as 62, Fig. 6, or with the thin edge of the metal itself, as 63. Made inthis manner, simply the sharp edge of the disk requires to be ground to a surface, the yield of its center insuring proper fluid-tight contact on the valve-seat.

In practice valves have been formed in the manner just described from sheet metal, but

I five one-thousandths of an inch in thickness.

Parenthetically, it may be stated that the difference in pressurebetween the ingress and egress sides of the valve is wholly dependent upon the friction developed from all causes in the operation of the meter as a whole.

As we have in practice reduced the work- 'ing-pressure, in certain instances,to less than two, one-hundredths of a poundv per square inch of area, it will be apprehended that there can be no possibility of the thin elastic valve being collapsed upon itself from this or any analogous cause.

' To prevent the valve-spindle from working apartwhere screwed together, we slot the outer end, as at 64, and insert a pin, 65, in the faceplate bearing,said pin passing freely through the said slot. The thrust-block is also keyed or pinned to the front bearing of the spindle; hence the entire structure, when in operative position, is locked against the accidental disarrangement of its parts, which is likely to occur, as is'well known,in structures bound by screws and subject to the-effect of percussion.

To realize the greatest economy of space it is necessary to pass the piston-rod through the valve-casing as near as may be to the valve-ports,and when the valve-casing is constructed as small as may be and serves its several functions, this sets the crown or up per portion of the cylinder eccentric to the main body of the cylinder, as indicated in full lines of Fig.3 and dotted outline of Fig. 8. In this manner less metal is required in the formation of the cylinder.

The bearing for the piston-rod is formed through one of the partition-walls of the valvecasing, and in order to use iron in the cone struction of said valve-casing it becomes necessary that the said piston-bearing and the inner valve seats shall be of non corrosive metal. v

To obviate the cost of machining and fitting these parts, we so construct the core-box which forms the system of cores for the valve-casing as to receive and hold in proper position, as a part of the core system, the tube 67, which forms the bearing for the piston-rod and the inner valve-seats, as 66, Figs. 7 and 8. The core as a whole is then placed in the mold, and all of the parts enumerated are cast in the position they should occupy inthe valvecasing. Transverse slots, as- 68, Fig. 7, may be cut in the periphery of the said valve-seats to prevent them from turning when being milled off; but to insure a water-tight union of the valve-seats to the iron partitions, and in view of the fact that brass orbronze is superior to iron as an absorbent of heat, and that it will therefore become very hot, and will contract to a greater degree than theiron when cold, we form the periphery of the said seats in any of the modes shown, as at 69 70 71. In this wise the superior contraction of the composition will simply tend to hug the iron with the greatest intimacy. If formed as plain annuli,they would shrink away from the iron and be loose, and therefore useless for the duty intended.

With respect to the tube 67, as it is inclosed by iron on all sides through the valve-casing, it only requires to be held from displacement, to which end it may be'notched or grooved before inserting it in'the mold, or riveted or otherwise secured if not sufficiently pinched by the iron.

To permit the use of diaphragms of the thinnest and most flexile material, whether elastic or non-elasticas, say, pure sheet-rubber, gutta-percha, oiled silk, zylonite, or any rot-proof fabricwe form a pair of pressureways and intermediate sluice, the double (ones, 72 73, to the exact shape required to I give the proper displacement of fluid to a cer- I tain travel of piston. The conformation of the diaphragm at the terminus of each stroke assumes the frustum of a cone; hencethe pressure-cones are thus formed, each a duplicate of the other. The base of the diaphragm is secured between the bases of the frustums, and all are placed as one part between the flanges of the cylinders.

As shown in Fig. 8, the diaphragm is rolled within and upon the pressure-cones by each change of the current through the cylinder,and is practically freed from strain when actuating the valve mechanism.

It will be understood that the pressure-cones are formed from non-corrosive inelastic ma terial. I I

The piston is formed from two stamped disks, 74, whose normal shape is shown in Fig. 10. Each is a duplicate of the other. The perimeters 'ot' the disks are flanged, as at 75, and thereby form a rounded bearing for the diaphragm, and are stiffened against deflection from a horizontal plane. To insert and confine the diaphragm it is simply necessary to spring or buckle the centers of the disks inward toward each other and secure them by means of the hub and collar 75. Fashioned in this man ner,the pinch upon the diaphragm is perfectly uniform, regardless of how forcibly the collar and hub may be brought together, besides which the structure is made exceedingly stifi' from very light sheet metal, and is simple to construct and to assemble.

We do not limit ourselves to the arrangement of channels nor construction of valve shown, as it will be obvious that by bringing counteracting currents in any way upon a valveofthe construction described,or of other form, all tendency to drive the valve will be obviated. It will be apparent that the outer cylinder or casing may be of any desired form.

WVe do not herein claim, broadly, the valves shown and described, as they will form the subjectmatters of another application, and the omission of such claims herein is without prejudice to our rights to such inventions.

We claim- 1. The method of controlling the direction of fluid in a meter for the purpose of neutralizing the dynamic force of the currents upon the valve during the time of its transit, which consists in causing the ingress-fluid to pass to the valve in opposing directions of equal volumes, and also'in causing the egress-fluid to pass from the valve in opposing directions of equal volumes, substantially as described.

2. The double ingress water-Way and ingress-sluice, the double intermediate wateregress water-way and egress-sluice, said water-ways being formed in the cylinder and said sluices in the valve-casing, a valve operated within the valve-casing, and apparatus for alternating the position of said valve, all in combination substantially as set forth.

3. In a fluidaneter, the combination of the semicircular ingress and egress water-ways formed in a horizontal plane of a cylinder, a

pair of intermediate water-ways formed in a vertical plane of a cylinder, the common termini of which are connected with sluices formed in an internal valve-casing containing valve-ports, avalve, and means for alternating its position, said waterways and sluices being so disposed that any current passing to the valve comes from opposing directions, and any current passing from the valve leaves it in opposing directions, for the purpose of eliminating any effect upon the action of said valve due to the force or direction of currents through the meter, substantially as specified. 4. The double ingress, intermediate, and egress water ways, in combination with a valvecasing containing valve-ports and a valve, and means for actuating the valve to alternate positions, whereby the currents are subjected to equal deflections in equal volumes through passages of equal areas of crosssection, for the purpose of reducing the velocity of flow through the said waterways.

5. In a fluid-meter, the within-described outer casing, provided with semicircular water-ways, consisting of an open portion formed in the casing, as from 26 to. 2'7, closed by plates or covers, for the purpose specified.

6. The valve-casing having an ingress, an intermediate, and an egress sluice and valveports, each and all of said sluices passing longitudinally through the valve-casing and parallel with each other, and adapted to connect with corresponding openings in the maiucylinder, substantially as set forth.

7. In a fluid-meter, in combination with a valve, a piston, a rod connected to the piston.

and a positive val ve-actuating mechanism and double-acting valve-springs, all of which are interposed between the rod and the valve, the construction being such that at a point near the extreme part of the movement of the piston and rod they will coact with the springs to reverse the position of the valve at a greater ratio of movement than that of the said piston and-rod, substantially as described.

8. The combination, with a valve and apis' ton and rod, of a positive valve-actuating mechanism and doubleacting valve-springs, the construction being such that a small portion of the movement of the piston coacts with the springs at a multiplied ratio to impel the valve during the time of its reversal, substantially as specified.

9. In combination, the valve-spindle, upon which is mounted a valve, the multiplying lever, connected to the valvestem, the bellerank, and means for operating the same, said bell-crank and multiplying-lever being connected in such manner that any motion imparted by the bell-crank to the multiplyinglever will be multiplied in its action upon the valvestem, substantially as specified.

10. In combination, the valve spindle, upon which is mounted a valve, the multiplying lever connected to the valve-stem, the bellcrank, upon which is a carriage pivotally mounted, carrying toggle-springs, which act upon a thrust-block secured to the valvespindle, and means for actuating the bellcrank, the construction of the parts being such that the toggle-springs will be brought nearly or quite to their dead-centers before motion is imparted to the multiplying-lever, substantially as specified.

' 11. In combination, the bell-crank, upon which is formed a slotted arm, the multiplying-lever having a tooth or spur engaged by the said slotted arm, the valve-spindle connected with the multiplying-lever, and operating means, the relation of the said slotted arm and tooth being such that a certain degree of motion may be imparted to the bellcrank without actuating the multiplying-lever, but thereafter the continued movement of the bell'crank will impel the said multiplying-lever, substantially as specified.

12. The combinatiomwith a valve and a lever for operatingit, of the spring, formed in the manner shown and described, and for the purpose specified.

13. In a fluid-meter, the combination, with a valve-casing having fluid ways or passages, of abuilt-up valve consisting of two flexile metal disks the perimeters of which are cupped or flanged, and within which are placed disks of pliant packing, which form the contact-faces of the valve, and a washer of less diameter than and interposed between the said metal disks, whereby the fiexure of the 'disk is permitted,'as and for the purpose set forth.

14. The combinatiomwith a valve'chambcr of a fluid-meter, of abuiltup valve-spindle consisting of a central or main body having shoulders. and two end pivotal portions, each having ashoulder, and adapted to be screwed to the central portion upon an interposed valve, a portion of one or both of said pivotal portions being slotted longitudinally,said slot or slots engaging a projection in the bearing of the spindle,whereby the structure is locked against the accidental dislocation of its component parts, substantially as specified.

15. In a fluid-meter, the upper cylinder having a crown adapted for the reception of avalve-casing, of less diameter than the main portion (of which it is an integral part) and set eccentric to the same, for the purpose set forth.

16. The combination, with a valve-casing having valves operating therein, of a piston for operating the valves, 2. piston-rod, and a bearing for the rod, consisting of non-corrosive material embedded in the casing, sub-- stantially as described.

17. In a fluid-meter, a valve-casing formed of iron, having interior and exterior ports, of the inner valve-seats, being constructed of brass or bronze composition and embedded in the iron, the valve-casing and valve-seats having interlocking parts, substantially as described.

18. In a fluid-meter having a frustum-ofcone-shaped diaphragm of pliant material, the combination, with said diaphragm, of a piston constructed otl two metal disks, the centralportions of which, in their normal condition, are dished outward from each other, and means for securing the disks together at their centers, whereby when the said dished portions are brought together and secured the smaller rim of the diaphragm is held between the outer surfaces of the disks with a uniform compression of its substance, substantially as specified.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

CHARLES o. BAaTbN. JOHN THOMSON.

\Vitnesses:

' LYMAN I-I. Essnx,

WM. THoMsoN. 

